1. Field of the Invention
The present invention relates to a logic circuit diagram processing apparatus and a method of processing the logic circuit diagram, and more specifically to an apparatus for implementing a signal tracing operation such that signal path lines influenced by a designated original signal can be displayed in a different color, for instance.
2. Description of the Prior Art
Owing to the higher performance of graphic apparatus and lower price of engineering work stations (e.g. by use of a personal computer), recently there have widely been used logic circuit diagram editing apparatus by which a designer can draw or alter a digital logic circuit diagram or an automatic logic circuit diagram generating apparatus by which a logic circuit diagram can be drawn automatically on the basis of connection data (e.g. connection data or connection languages) represenative of mutual connection relationships between logic elements.
In these logic circuit diagram processing apparatus, however, there exists a need for checking the influence of a specific signal upon the logic circuit, as when an edited logic circuit is checked again after some days have elapsed or when a logic circuit diagram edited by another person is required to check.
In the prior-art logic circuit diagram processing apparatus, however, the functions are as follows: when a specific signal name is designated, coordinates of the associated signal lines are indicated on a circuit diagram or the associated signal lines are displayed in a different color on a circuit diagram (e.g. "Circuit diagram edit system provided with inquiry function" by Kawamoto, Information Processing Society Japan (IPSJ), DA 16-3, 1983). Therefore, in the case where an influence of a sigal upon a logic circuit is required to trace, the following steps are repeated: an original signal name is designated; the associated signal line is identified on the logic circuit diagram on the basis of a signal line corresponding function; other signal names connected to logic elements to which the associated signal lines are connected are designated, and the above signal line identifications on the logic circuit diagram are repeated on the basis of the signal line corresponding function until the identification reaches the output terminal or memory element of the logic circuit.
In a logic circuit having many stages from the input terminal to the output terminal, however, since signal names should be repeatedly designated while confirming the displayed signal lines, there exist problems such that troublesome work is repeatedly required and therefore mistakes may occur in signal name designation in proportion to an increase in the number of signal name designations, thus lowering the accuracy of a signal tracing operation.